Additives or other treatments to enhance the performance of absorbent sheet are well known in the art. There is disclosed in U.S. Pat. No. 6,074,525 to Richards a process for increasing bulk of a foreshortened fibrous web which includes adding moisture to the web at selected portions, thereby causing the crepe in those portions to relax. Among the functional additives which may be present in the added moisture, there are listed softeners, debonders, binders, polyhydroxy compounds, lotions, dispersions, anti-bacterial agents and so forth. See (Col. 10, lines 50-(Col. 11, line 5.
Polymer films have been used on paper products to enhance or provide barrier properties. Barrier performance of polymer films on paper substrates is a complex process and is influenced by the wicking effects in the paper. Films may be applied to paper by extrusion or the like or by way of a latex. See FUNDAMENTALS OF BARRIER PROPERTIES, Stannett, V. T. et al., Department of Chemical Engineering, North Carolina State University, Raleigh, N.C. (undated). Dispersion coating is likewise known. For example, there is shown in EP 1 103522 A1 a process is disclosed for application of a polymer coating on a granular activated carbon to essentially eliminate or significantly reduce attrition by dusting without a reduction in absorptive velocity or capacity of the activated carbon. The coatings applied include a high density polyethylene dispersion and a silicone dispersion. See EP 1 103522 A1 at page 5, lines 10 and following.
Composite structures including paper layers are often used in products requiring a variety of attributes in the overall performance of the product. This is so, in part, because an open paper structure will have good liquid acquisition properties but poor distribution properties. Multiple layers may accordingly be employed in some absorbent products which require a spectrum of properties. One non-woven described in SMART MATERIALS FOR LIQUID CONTROL, Non-Wovens World, October-November 1999, Dyrmose-Peterson, pages 95-99 includes an upper cover stock layer thermally bonded to a layer combining both desirable liquid acquisition and distribution properties.
Likewise, composite structures have been used as bed pan liners for example. See U.S. Pat. No. 3,546,716 to Laumann. The bed pan liner described in the '716 patent includes generally a cold water-soluble base film of synthetic polymeric material, a water insoluble or water repellant coating on one side of the base film and tissue paper covering and adhered to the insoluble coating.
So also, a sheet product including a substrate of non-woven cellulosic fibers, a discontinuous prime coating of hydrophobic material adhering to the cellulosic fibers and a second hydrophilic material filling the surface voids between hydrophobic material deposits is described in U.S. Pat. No. 3,607,348 to Wray et al. The dual coatings described in the '348 patent render the paper relatively impermeable.
There is described in U.S. Pat. No. 5,399,366 to Geddes et al. multi-layer packaging for hot food. The package includes an absorbent layer for disposing adjacent the hot food, an extruded barrier film layer adjacent the absorbent layer and an outer paper layer adjacent the barrier layer. The absorbent layer keeps moisture and grease away from the hot food (employing a partially hydrophobic or a low-capacity sub-layer) while the barrier layer prevents soak through and retains heat. Various polymers and waxes are used in the impermeable layer. See also U.S. Pat. Nos. 5,560,945; 5,585,129; and 5,609,901 also to Geddes et al.
There has been employed in connection with absorbent paper structures, various means to increase water resistance. There is disclosed in U.S. Pat. No. 1,682,346 to Lorenz a multi-layer paper sheet for wash cloths and the like which will not dissolve during use. At least one layer is made from pulp which has been sized with resin or latex to impart water resistance. Indeed, paper structures have been modified or combined with layers of polymer films in a variety of ways to enhance performance or provide performance attributes not attainable with paper alone. There is disclosed in U.S. Pat. No. 3,654,064 to Laumann a multi-layer structure including layers of tissue paper and wax for providing a disposable barrier pro duct. In general, the wax or polymer layer is applied to the paper substrate by way of extrusion coating. See Col. 4, lines 14 and following. In U.S. Pat. No. 3,612,054 to Matsuda there is disclosed a sanitary napkin including a plurality of layers of absorbent material and at least one barrier sheet of liquid repellant material interposed between absorbent layers. The barrier sheet is reported to improve distribution of liquid within the absorbent material. U.S. Pat. No. 4,117,199 to Gotoh et al. discloses a coated paper having a moisture and water-proof coating thereon produced by coating a paper substrate with an aqueous dispersion containing a synthetic rubber latex and a wax dispersion in various amounts. See Col. 3, lines 25 and following.
U.S. Pat. No. 4,349,610 to Parker discloses a method for improving the water repellency of a naturally porous, moisture containing paper web by treating the web with a coating composition containing as its active coating ingredient an alkyl alkoxysiloxane which reacts with the moisture contained in the paper web to produce a polymer.
U.S. Pat. No. 4,786,367 to Bogart et al. discloses a soft, absorbent and bulky cellulosic fibrous web which has been treated to impart a soothing or emollient effect to the human skin when used for wiping and drying. The agent applied to the web is a lauroamphoglycinate.
U.S. Pat. No. 4,601,938 to Deacon et al., discloses paper towels which have been impregnated with a liquid composition. Migration of the liquid along the length of the paper substrate is substantially prevented by dividing the substrate into a plurality of individual areas by means of a repeating pattern of liquid-repellant barrier material, for example, wax or certain resins, extending across the width of the substrate.
U.S. Pat. No. 4,789,564 to Kanner et al. discloses that paper may be treated with certain hydridoaminosilanes in order to render the materials water-repellant.
U.S. Pat. No. 4,816,320 to St. Cyr discloses a multiply tissue for use as cleansing, facial or toilet tissue combining at least one and preferably two, soft, absorbent layers of loosely felted cellulose fiber paper and an overlying layer of thin, light-weight moisture resistant cellulose fiber paper with non-skid traction material overlying the moisture resistant layer. The traction material may be a layer of cellulose fiber paper having a roughened overlying surface or may have an outer coating of finely divided latex particles applied to the overlying surface of the moisture resistant layer or to a separate, overlying layer. The moisture-resistant layer may be, for example, a layer of glassine paper. See Col. 2, lines 50-55.
U.S. Pat. No. 4,950,545 to Walter et al. discloses facial tissue containing a silicone compound exhibiting improved softness and reduced lint while maintaining absorbency. According to the disclosure, the silicone compound is added in an amount of from about 0.1 to about 5 weight percent. See Col. 1, lines 40-45. See, also, U.S. Pat. No. 5,227,242 to Walter et al.
In U.S. Pat. No. 4,987,632 to Rowe et al. discloses an absorbent wiping towel suitable for use in cleaning soiled surfaces in the presence of water which includes an absorbent substrate, such as paper, having applied thereon a moisture barrier to cover at least 10% of the total area of each side of the sheet in such a manner that the moisture barrier on one side of the sheet coincides with the moisture barrier on the opposite side so as to form a sandwich. Examples of moisture barrier material include wax dispersions applied to the sheet. See Col. 7, lines 40 and following.
There is disclosed in U.S. Pat. No. 5,449,551 to Taniguchi a fibrous web such as tissue paper and non-woven fabrics containing at least one kind of hygroscopic material such as polyhydric alcohols or sugars exhibiting hygroscopicity. According the '551 patent the hygroscopic material renders the tissue softer and increases the adhesiveness between fibers, thereby reducing lint.
In U.S. Pat. No. 5,552,187 to Green et al. there is disclosed a fibrous mat-faced gypsum board coated with a water-resistant resinous coating. A preferred resin for use in connection with these structures is available in the form of a latex sold by Unicol Chemicals Division of Unicol Corporation under the mark 76 RES 1018. The pH and solids content of the latex are respectively 7.5-9 and 50%. The resin is a styrene acrylic copolymer which has a relatively low film forming temperature and a Tg of 22° C. See Col. 9, lines 57 and following.
There is disclosed in U.S. Pat. No. 5,601,871 to Krzysik et al. a soft, uncreped through dried tissue product having uniformly distributed surface deposits of a chemical composition which imparts a reduction in skin irritation during use. Suitable compositions are those which have a melting point of from about 30° C. to about 70° C. and are applied to the outer surface of the tissue product in melted form, preferably by rotogravure printing. A suitable composition contains an oil, a wax and preferably a fatty alcohol. Add-on rates may be from about 1% to about 40 weight percent of the product. See Col. 3, lines 12 and following.
In some embodiments, the product of the '871 patent is characterized by its hydrophobicity which helps prevent “wet-through” to the users hand during use. This property can be measured in accordance with U.S. Pat. No. 4,950,545 noted above. See also U.S. Pat. Nos. 5,614,293 and 5,650,218 to Krzysik et al. as well as: U.S. Pat. No. 5,665,426 to Krzysik et al. which discloses a tissue product having uniformly distributed surface deposits of a solidified composition having a melting point of from about 30° C. to about 70° C.; and U.S. Pat. Nos. 5,885,697 and 6,187,695 both to Krzysik et al. all of which references disclose tissue products having disposed thereon surface deposits of a solidified composition having a melting point of from about 30 to about 70° C. Such compositions include in melted form oils, waxes, and the like. The additive is reported to enhance the feel of the tissue upon the skin.
In U.S. Pat. No. 6,267,842 to Ona et al. there is disclosed a water-based treatment agent for application to tissue paper which suppresses a feeling of slipperiness or wetness in ordinary tissue paper so that the paper has a dry touch, ample smoothness and a clean, smooth, tactile impression. The treatment agent includes a silicone oil dispersion in which cross-linked silicone particles of a specified size contained in the silicone oil droplets are dispersed in water and applied to the tissue. See Col. 10, lines 5 and following.
There is disclosed in U.S. Pat. No. 5,716,692 to Warner et al. a lotioned tissue paper. The lotion composition is applied to the tissue in amounts of from about 5 to about 15 percent by weight. The lotion composition includes plastic or fluid emollient such as petrolatum, a mixture of petrolatum with alkyl ethoxylate emollient and an immobilizing agent such as a fatty alcohol or a fatty acid to immobilize the emollient on the surface of the tissue paper web and optionally a hydrophilic surfactant to improve wettability when applied to the tissue.
Various additional methods of influencing liquid migration in a web or composite structures are disclosed in the following U.S. Pat. Nos. 5,658,639 to Curro et al.; U.S. Pat. No. 5,695,487 to Cohen et al.; U.S. Pat. No. 5,792,404 to Cree et al.; U.S. Pat. No. 5,849,000 to Anjur et al.; U.S. Pat. No. 5,932,316 to Cree et al.; U.S. Pat. No. 6,015,935 to LaVon et al.; U.S. Pat. No. 6,025,049 to Ouellette et al.; U.S. Pat. No. 6,046,378 to Quincy, III et al.; U.S. Pat. No. 6,107,539 to Palumbo et al.; U.S. Pat. No. 6,180,052 to Ouellette et al.; U.S. Pat. No. 6,231,948 to Ouellette et al.; U.S. Pat. No. 6,232,521 to Bewick-Sonntag et al.; U.S. Pat. No. 6,383,960 to Everett et al.; U.S. Pat. No. 6,403,858 to Quincy, III et al.; and U.S. Pat. No. 6,416,628 to Huang et al. Curro et al. '639; Cree et al. '404, Cree et al. '316, Oullette et al. '049, '948 and '052, and Bewick-Sonntag et al. '521 relate to increasing the moisture penetration into a web by making a surface more hydrophobic. Anjur et al. '000 report greater permeability when a wettable staple fiber is used with a wettable binder fiber, while La Von et al. enumerates advantages of having enhanced vertical wicking in the crotch area of certain absorbent products and Cohen et al. disclose corrugated structures for increasing Z-direction liquid transport. So also, it is seen in U.S. Pat. No. 6,046,378 to Quincy, III, et al. that wettability of synthetic fibers is increased by altering their surface properties; in this respect, see also Quincy, III, et al. '858, as well as Palumbo et al., '052. The '960 Everett et al. patent discloses composites including superabsorbent polymers and finally with respect to the patents noted in this paragraph, Huang et al. '628 relates to paperboard impregnated with hydrophobic rosin.
Perhaps more pertinent to the discussion which follows are the references noted below.
U.S. Pat. No. 6,332,952 to Hsu et al. discloses a tissue with strikethrough resistance provided by way of a water-repellant agent such as sizing agents, waxes, or latexes. Col. 1-2. The sizing agent is added in an amount of from about 0.5 to 10 pounds per ton of fiber, e.g., from about 0.025 to about 0.5 percent by weight, Col. 2, lines 42-46. In some embodiments, the tissue does not contain permanent wet-strength binder resins such as polyamide epichlorohydrin resins. Col. 6, lines 2-11, and the sizing is sprayed on the tissue after the product is creped from a Yankee dryer, or wax, for example, may be added to the furnish before it is applied to the forming fabric by way of a layered headbox. The only repellant agent exemplified is an alkyl ketene dimer. There is disclosed in related PCT publication No. WO 00/00698 (Application No. PCT/US99/14402) a toilet tissue product including a first cellulosic ply and a second cellulosic ply at least one of which has been treated with a repellant agent to prevent fluid from striking through the tissue product. The repellent agent is added in an amount of from about 1 to about 30 pounds per ton of fiber; and more specifically from about 1.2 to about 20 pounds per ton of fiber. See Publication No. WO 00/00698 at page 2, lines 8 and following.
U.S. Pat. No. 6,027,611 to McFarland et al. discloses a process by which facial tissue is rendered resistant to water penetration by treating the fibers with a sizing agent prior to forming the sheet, or typically after the sheet is formed. The sizing agent is added in an amount of from about 1 to about 10 pounds of sizing agent per ton of fiber in the tissue, that is, up to about 0.5 weight percent. See, Col. 2, lines 22-26. Typical products have an absorbency rate of from 100-400 second. See, Cols. 2-3.
In U.S. Pat. No. 6,054,020 to Goulet et al. there is disclosed tissue and towel products which resist moisture. Moisture-resistance is imparted by way of amine-modified polysiloxane compounds applied to the outer surfaces of the web. The amount of amine functionality may be controlled to adjust hydrophobicity to the desired levels which delay, however, allow moisture penetration into the tissue. The siloxane may be typically applied in the form of an dispersion. Add-on rates are specified to be from about 0.1 to about 5 weight percent. Col. 4, lines 12-19. The products of the '020 patent are reported to have characteristically long wet-through times and relatively large wet-out areas.
U.S. Pat. No. 5,851,352 to Vinson et al. discloses a multi-ply tissue product provided with an internal surface which has deposited thereon a strength agent in an amount of form 0.5 to 10% by weight. The only strength resin exemplified is an acrylic latex applied by way of direct roto-gravure printing. See Column 25, line 43 and following. Note also a number of water-soluble materials are enumerated in Col. 7, line 55 and following.
U.S. Pat. No. 6,066,379 to Ma et al. discloses a repulpable, water-resistant paperboard provided with a water-repellant coating which includes a polymer matrix, wax and pigment mixture. The paperboard is particularly well-suited for corrugated products. The water-repellant coatings are reported to form pinhole-free coatings (Col. 8, line 10 and following) and are applied in amounts of from about 2-3 weight percent of the weight of the paperboard.
U.S. Pat. No. 5,858,173 to Propst, Jr. discloses coating cardboard and the like with an aqueous acrylic/wax dispersion mixture to provide grease and water resistance. A typical mixture includes 15 parts of a high viscosity aqueous acrylic resin dispersion, 65 parts of a low viscosity aqueous acrylic resin dispersion and 6 parts of an aqueous polyethylene wax dispersion. The mixture is applied upstream of the headbox, in the headbox or downstream of the headbox by spraying, for example. According to the patent, more or less than 3.0-20% by weight of the aqueous composition can be incorporated into the stock or finished paper. Col. 4, line 4. According to the '173 patent, the described product is repulpable.